Lutein 3’-methyl ethers

Fig. (26). Formation of lutein 3 -methyl ethers from lutein (25).

Allylic cations have been hypothetical intermediates in various common reactions with carotenoids, formed in acidic media in SNl-type reactions. Two typical examples are mentioned here. Lutein (25) provides selectively the two C-3 methyl ethers (VR and 3 ) upon treatment with acidic methanol [146], The stereochemical result is compatible with an intermediate, planar, allylic cation, Fig. 26. 

Lutein isomers Marigold C30 MS Methanol/tert-butyl methyl ether/water [8]... 

Extracts were further purified on neutral alumina cartridges conditioned by passing through 5 ml of hexane. Extracts were loaded in hexane and washed by 5 ml of hexane. The at- and /1-carotenes were removed by 3.5 ml of acetone-hexane (10 90, v/v), other carotenoids were eluted with acetone-hexane 30 70 and 70 30 v/v. Prepurification of pigments was performed in subdued light under a stream of nitrogen. Analyses were carried out in a C30 column (250 X 4.6 mm i.d., particle size 5/tm) using isocratic mobile phase composed of methyl-ferf-butyl ether (MTBE)-methanol (3 97 and 38 62, v/v) at a flow rate of 1 ml/min. The column was not thermostated separations were achieved at room temperature (about 23°C). Carotenoids were detected at 453 and 460 nm (lutein). The... 

Fig. 11 HPLC of carotenoids solvent-extracted from (A) raw and (B) thermally processed carrots. Column, 5-/um polymeric C1(J (250 X 4.6-mm ID) mobile phase, methyl tert-butyl ether/methanol (11 89), 1 ml/min absorbance detection, 453 nm. Tentative peak identifications (1) all-trans-lutein (2) 13-cis-a-carotene (3) a cis-a-carotene isomer (4) 13 -cA-a-carotene (5) 15-cis-/3-carotene (6) 13-cis-/3-carotene (7 and 8) cis-fi-carotene isomers (9) all-frans-a-carotene (10) 9-cis-a-carotene (11) all-frans-/3-carotene (12) 9-ci. -/3-carotene. (Reprinted with permission from Ref. 192. Copyright 1996, American Chemical Society.)...

In an excellent article by Bell et al. [356], the retention of 12 carotenoids (zeaxanthin, lutein, echinenone, / -cryptoxanthin, and a-, 9-cis-a-, 15-cis-a-, 9 -cis-a-, 13-cir-a-, ] -, 3-cis-P-, and 15-c/j- -caiotene) was studied with respect to temperature (277 K to 323 K) on C,g, C30, and C34 columns (A = 450 nm). Methanol was used as a mobile phase on the C g column and 95/5 methanol/methyl r-butyl ether on the C30 and C34 columns. The authors noted that acetonitrile was a potential mobile phase modifier but that high acetonitrile levels ofien led to decreases in recoveries. The use of dichloromethane was discouraged since residual HCI due to natural solvent degradation was implicated in poor recoveries as well. The latter is supported by the fact that low molecular weight alkenes are ofien used as preservatives in dichloromethane. A series of van t Hoff plots (essentially Infc vs. 1 /T) were presented where C]g phase showed near linearity and C30 and C34 phases exhibited nonlinear relationships for most carotenoids. 

Violaxanthin, lutein isomers, a-, P-carotene Grapes C30 MS Triethylamine, methanol, water, methyl tert-butyl ether [44]... 

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